IRVINE — Support appears to be waning in Orange County for a controversial statewide measure on the November ballot that offers parents of school-age children a taxpayer-funded voucher to help pay private school tuition, according to the results of a new poll released Wednesday.

The 1993 Orange County Annual Survey conducted by UC Irvine found Proposition 174, the school voucher initiative, was favored by 44% of the county's registered voters and opposed by 42%. That result was down sharply from a Times Orange County Poll in June that found voters in favor of the plan by nearly a 2-to-1 margin.

The UCI survey conducted by professor Mark Baldassare and Cheryl Katz also found strong support in this traditionally tax-wary county for another initiative on the Nov. 2 ballot that would extend a half-cent sales tax to help pay for public safety costs.

Out of more than 800 registered Orange County voters who were polled in late August, 57% said they favored the sales tax plan in Proposition 172 while 35% opposed it. The poll of voters had an error margin of plus or minus 3.5%.

The results stood in contrast to an independent statewide poll conducted last month by Mervin Field that found California voters almost evenly split on the sales tax issue.

The school voucher plan in Proposition 174 would change the way the state funds education by providing parents with vouchers--worth about $2,600 for each child--to be redeemed at any public, private or parochial school. Supporters maintain that the measure would allow students to escape poor schools, but critics insist it would only widen the gap between good and bad schools.

Statewide, the recent Field poll found the school voucher initiative is already in trouble with 46% of registered California voters opposed to the plan and 36% in support. Baldassare said the UCI poll results could spell more trouble for the idea since its backers are counting on heavy support from conservative areas such as Orange County.

He said the drop in support for the measure since The Times Orange County survey in June--also conducted by Baldassare--was probably due to growing fears that taxpayers would have to pick up the $2,600 tab for each child wanting to attend private school.

The estimated $2,600 for the vouchers is based on half the amount California taxpayers already spend for each student in public school. But Proposition 174 critics insist that the measure contains hidden costs that would also be borne by taxpayers.

"In today's economic climate, any concerns like that are likely to erode support for a measure that would otherwise seem popular," Baldassare said.

The turnout in the November election is expected to be low because there are no candidates on the ballot to attract attention.

Among the voters in the Orange County survey who said they were most likely to participate in the November election, support for Proposition 174 was even shakier with 42% in favor of the measure and 44% opposed to it. Opposition was strongest among Democrats and older voters, the poll found.

But Sean Walsh, a spokesman for the "Yes on 174" campaign, said he was not bothered by the poll results.

"Actually, I find it good news," he said of the Orange County poll results. "It shows that we're in a horse race here. It's neck and neck and we will be continuing to take our message to the voters of this state, and we are confident that Orange County and other counties will support us."

But John Smith, a training specialist with the California Teachers Assn. in Orange who has been active in the effort to defeat Proposition 174, said he expects opposition to the voucher plan will grow.

"Once the public learns what Proposition 174 will do and won't do, a lot of people will do an about-face," he said. "The idea sounds good on the surface, but No. 1, it will not improve public schools, and No. 2, the (private) schools that currently could qualify for vouchers would be taking public money and putting it into private schools."

Proposition 172--the Local Public Safety Protection and Improvement Act--would permanently extend an existing half-cent sales tax that is now set to expire in January. The money would be used to help pay for local police, fire protection, jails and district attorneys.

Despite Orange County's reputation as an anti-tax community, Sheriff Brad Gates said Wednesday that he is not surprised by the strong support for Proposition 172 found in the UCI poll.

Gates said the results--showing wide support for the measure across virtually all political, economic and age categories--matched the findings of private statewide polls taken by law enforcement groups hoping to pass the measure.